A semiconductor device for power conversion such as a switching element is formed by connecting active elements in parallel. The active element may be a transistor or a diode. Since each active element heats, temperature of the active element increases. Increasing the temperature causes degradation of performance and destruction of the active element. Therefore, it is important for the active element to inhibit increasing the temperature.
Some techniques to inhibit the temperature are disclosed in JP-A2008-182122(KOKAI) and JP-A2007-27440(KOKAI). These references try to uniform the temperature in a chip by providing a space having no active element on the chip.
On the other hand, the semiconductor device for power conversion is better to have high breakdown voltage and low on resistance. It may be effective to use material having high critical electric field strength in order to achieve the high breakdown voltage. A wide-gap semiconductor may be preferable as the material having high critical electric field strength. Some techniques to use the wide-gap semiconductor for the semiconductor device of the power conversion are disclosed in JP-A2003-229566 (KOKAI) and JP-A2007-180454(KOKAI). In these references, the transistor and the diode are formed by nitride semiconductors which are one of the wide-gap semiconductors. The transistor and the diode are formed on a substrate as power converting elements.
It is important for the semiconductor device of power conversion to inhibit a maximum temperature in order to reduce degradation of performance and keep reliability. However, the conventional technique that heat is dispersed spatially may not enough to inhibit increasing the temperature of the active elements. Moreover, the conventional technique that the space having no active element exists in the chip causes increasing of chip area and cost.